The present disclosure relates generally to variable vane systems for a gas turbine engine, and more particularly to a system for positioning variable vanes within a gas turbine engine.
Gas turbine engines include a compressor section, a combustor, and a turbine section that operate in conjunction with each other to generate thrust. The compressor section, the combustor, and the turbine section are connected via a primary flowpath passing through each section. Disposed within the primary flowpath are multiple stators and rotors that affect the airflow through the primary flowpath, and aid in the proper functioning of the combustor section and the turbine section. In some examples, other features of the gas turbine engine result in undesirable flow characteristics.
In order to correct the undesirable flow characteristics, gas turbine engines typically include variable vanes positioned within the primary flowpath to alter the airflow. In some examples, the vanes can be repositioned or reoriented depending on the particular operating state of the gas turbine engine, or other airflow characteristics of the air flowing through the primary flowpath. Vanes of this type are referred to as variable vanes. The variable vanes are connected to a synchronization ring that synchronizes the reorientation of all the vanes connected to the ring. Some existing gas turbine engines include more than one synchronization ring, with some variable vanes connected to each of the synchronization rings.
In some existing systems, the orientation of the variable vanes is controlled by a single actuator that may be located outside of an engine casing. The actuator rotates the synchronization ring, and the rotation of the synchronization ring is transferred to all of the connected variable vanes simultaneously. As a result of natural spring constants in the synchronization ring, deflection occurs in the synchronization ring, and the orientation adjustment of all the vanes due to the rotation is not identical. In particular, the farther a vane is from the actuator, the more the vane is skewed from the desired orientation due to deflection.
In order to reduce the deflection, some systems incorporate additional actuators, offset from the first actuator. The additional actuators are also connected to the synchronization ring and are controlled by the first actuator. During operation, the additional actuators are slave actuators to the first actuator and impart the same motions onto the synchronization ring as the first actuator. The additional actuators are also positioned outside of the engine case, and includes a component protruding through the engine case resulting in additional protrusions through the engine case. The additional protrusions are particularly detrimental in engine designs having multiple concentric cases as a single protrusion penetrates each of the concentric cases. Furthermore, in certain examples, the additional actuators are positioned in inaccessible areas of the gas turbine engine.